1. Field of the Invention
The present invention relates to an organic light emitting display, and more particularly to an organic light emitting display that can display an image of uniform brightness.
2. Discussion of Related Art
Recently, various flat panel display devices have been developed to substitute for a cathode ray tube (CRT) display because the CRT display is relatively heavy and bulky. Flat panel display devices include liquid crystal displays (LCDs), field emission displays (FEDs), plasma display panels (PDPs), organic light emitting display devices, etc.
An organic light emitting display device is a flat display device that displays an image using an organic light emitting diode that generates light by the recombination of electrons and holes. Such an organic light emitting display device has advantages in that it has a high response speed, and operates with a low power consumption.
FIG. 1 is a view showing a conventional organic light emitting display device. With reference to FIG. 1, the conventional organic light emitting display device includes a display region 30, a scan driver 10, a data driver 20, and a timing controller 50. The display region 30 includes a plurality of pixels 40 coupled with scan lines S1 to Sn and data lines D1 to Dm. The scan driver 10 drives the scan lines S1 to Sn. The data driver 20 drives the data lines D1 to Dm. The timing controller 50 controls the scan driver 10 and the data driver 20.
The timing controller 50 generates a data drive control signal DCS and a scan drive control signal SCS according to externally supplied synchronous signals. The data drive control signal DCS generated by the timing controller 50 is provided to the data driver 20, and the scan drive control signal SCS is provided to the scan driver 10. Furthermore, the timing controller 50 provides externally supplied data Data to the data driver 20.
The scan driver 10 receives the scan drive control signal SCS from the timing controller 50. Upon the receipt of the scan drive control signal SCS, the scan driver generates a scan signal, and sequentially provides the generated scan signal to the scan lines S1 to Sn.
The data driver 20 receives the data drive control signal DCS from the timing controller 50. Upon the receipt of the data drive control signal DCS, the data driver 20 generates a data signal (predetermined voltage), and provides the generated data signal to the data lines D1 to Dm in synchronization with the scan signal.
The display region 30 receives a first power of a first power supply ELVDD and a second power of a second power supply ELVSS from an exterior, and provides them to respective pixels 40. Upon the receipt of the first power of the first power supply ELVDD and the second power of the second power supply ELVSS, each of the pixels 40 controls an amount of current flowing into the second power supply ELVSS from the first power supply ELVDD through an organic light emitting diode corresponding to the data signal, thus generating light corresponding to the data signal.
That is, in the conventional organic light emitting display device, each of the pixels 40 generates light of a predetermined luminance corresponding to the data signal. However, due to non-uniformity of threshold voltages and a deviation of electron mobility of transistors included in each pixel 40, the conventional organic light emitting display device has a problem in that it cannot display an image of a desired (or uniform) luminance. In practice, threshold voltages of transistors included in each of the pixels 40 can be compensated to some degree by controlling a construction of pixel circuits included in the pixels 40, but a deviation of electron mobility cannot be compensated. In order to solve the problem, an electric current (instead of a voltage) can be supplied as a data signal. In practice, when the electric current is supplied as the data signal, although the transistors have non-uniform voltage-current characteristics, the organic light emitting display device can display a uniform image at the display region 30.
However, because the current supplied as the data signal is a minute current, it takes a long time to charge a data line. For example, assuming that a load capacitance of the data line is 30 pF, a time of several ms is required to charge a load of the data line by a data signal ranging from several tens nA to several hundreds nA. Upon considering one (1) horizontal period of several tens μs, a charge time of several ms may be too long. Therefore, an organic light emitting display device capable of displaying uniform brightness with a fast response time is still required.